Dynamic modelling and stability analysis of buck converter–based solar PV charge controller in low-voltage DC applications

Abstract

The maximum power extraction (MPE) from a solar PV panel depends on the maximum power point tracking (MPPT) algorithm and the connected PV power optimizer. For the effective MPE, precise MPPT algorithm and power optimizer needs to be designed. To facilitate this design, a detailed mathematical model of the solar PV power optimizer system is needed for understanding the effect of various power electronic components on stability and their behaviour in dynamic operating conditions. This paper presents a detailed small-signal modelling and stability analysis of buck converter–based solar PV power optimizer in continuous and discontinuous conduction modes for low-voltage DC (LVDC) applications. The small-signal modelling is developed by considering the PV power optimizer’s input filter capacitance and equivalent series resistance (ESR) of the power electronic components. A lucid analysis on the effect of input filter capacitance on PV power optimizer’s stability is presented. From the theoretical analysis and experimental validation, it has been observed that the MPPT in buck converter–based PV power optimizer is open-loop stable. A pole-zero cancellation in the transfer function of PV current to the duty cycle (I_PV) under both continuous and discontinuous conduction modes is observed, which leads to resiliency in the PV system’s stability for any variations in input capacitance.